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Date: Fri, 27 Jul 2012 14:31:00 -0400
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From: Warren Ziegler <wd2xgj@gmail.com>
To: rsgb_lf_group@blacksheep.org
Subject: Re: LF: Kites
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Stefan,
   I saw this Youtube video of 4 big guys trying to bring down a kite
like yours:
http://www.youtube.com/watch?v=3DK7q34sw4XMo

  I would love to try this but I live in an area densely covered with
tall trees, and it would be quite a drive to an open area where I
could launch an antenna (children's playground is not a good place for
a HV antenna!)

73 Warren K2ORS


On Thu, Jul 26, 2012 at 4:48 PM, Stefan Sch=E4fer
<Stefan.Schaefer@iup.uni-heidelberg.de> wrote:
> Hello Warren,
>
> Am 26.07.2012 19:39, schrieb Warren Ziegler:
>
>> Stefan,
>>       I imagine that a LF or VLF small vertical is a relatively high-Q
>> circuit, how do you manage to keep the kite vertical in resonance and
>> matched while the kite bounces around in the wind?
>>
> Most of the time the kite was quite stable, i.e. the angle and so the C d=
id
> not change significantly. The antenna current is stable within a 10% limi=
t.
> When the wind was poor in some situations, the kite drops to a lower angl=
e.
> Then the falling ERP is rather affected by the lower effective height tha=
n
> by the changing current. The current (say 1A on 8970 Hz) can easyly drop =
to
> 400 mA when the angle changes from 80 deg to 40 deg.
> One method is to compensate this by turning the variometer from time to t=
ime
> or you can use a working point of the variometer that uses a slightly to =
low
> L. Then the antenna current does not reduce when the kite falls (in certa=
in
> limits of course). This is the case because the little generator that i u=
sed
> (up to 550 W RF power in the best times) can be seen as something like a
> constant power source. So if the kite falls then slightly, the working po=
int
> moves to the peak of the resonance curve and the rotation speed is somewh=
at
> lowered. It was funny to observe this effect for many hours on the field =
:-)
> But normally the movement of the wire does not strongly change the antenn=
a
> current.
>
> OK?
>
>
> 73, Stefan/DK7FC
>



--=20
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1